Welcome to the Q&A Forum

Ouch.  That's a tricky one, but a 302 is likely your best bet if you HAVE to move to the new domain and then move them back to new URLs on the old domain with a 301, but why do the middle step of moving these pages to the new domain?  If you're going to put them on new URLs on the old domain, why not just create those URLs and move the pages there?  Any competent developer should be able to work around having pages on a domain remain live while development takes place in the background.  Really the only instance I could see of having to part with your domain for a few months is if you lost ownership of it, other than that, I'd do what I could to avoid bouncing around on domains, especially as far as a brand is concerned.

When you say you are running a cpa model is that "Focus on conversions (Conversion Optimizer)"  in google adwords on the search network? If So Then they are correct google is still using its regular algorithm which includes quality score they just make the management changes for you based on data